1. Field of the Invention
This invention relates to an automobile AC generator system and more particularly to an automobile AC generator system for converting the electric power produced by a generator driven by an automobile engine into ac electric power of desired characteristics, thereby enabling selective supply of electric power to a three-phase load or a single-phase load.
2. Description of the Prior Art
In today's automobiles, the compressor of the air conditioning system is powered by the automobile engine via a belt or the like. That is to say, the power transmission mechanism for the compressor is based on a mechanical linkage between the compressor and the engine.
An alternative system is proposed in Japanese Patent Public Disclosure No. 63(1988)-253897 (U.S. Pat. No. 4,973,856), which describes an automobile generator apparatus for supplying 120 volt ac power at commercial line frequency.
The proposed apparatus is illustrated schematically in FIG. 7. Reference numeral 21 in this figure designates a single-shaft, dual-output generator driven by an engine 1. It is a dual-voltage, high-frequency generator capable of producing a plurality of different voltage outputs. The low-voltage output of the single-shaft, dual-output generator 21 is supplied as low-voltage dc power to a battery 5 through a low-voltage output terminal 41. On the other hand, the high-voltage output of the single-shaft, dual-output generator 21 is supplied as three-phase, high-voltage ac power to a high-voltage output terminal 42, from which it is supplied through a connector box 43 to an inverter 44 for conversion into single-phase 120 volt ac power of commercial line frequency (60 Hz), and then is made available at an outlet 45 for the operation of a home electrical appliance or other such single-phase load.
As shown in FIG. 8, the single-shaft, dual-output generator 21 is, for example, of the three-phase synchronous type having first coils 46a for high-voltage output paired with second coils 46b for low-voltage output, the members of each pair of first and second coils 46a and 46b being serially connected (or wound in parallel) and overlaid in the same slot of the stator. One end of the coils of each phase are connected to a center point C of a star connection. A rotor having a field coil 47 is provided so as to rotate within the stator so that induced voltages can be produced in the first and second coils 46a, 46b by supplying field current through a field current supply terminal 48. The output of the first coil 46a is made available at the high-voltage output terminal 42, while the output of the second coil 46b is converted to dc power by a rectifier 49 and then made available at the low-voltage output terminal 41.
Overall control of the apparatus is conducted by a controller 50 having, inter alia, a voltage control circuit for controlling the voltages produced by the single-shaft, dual-output generator 21, a misoperation prevention circuit and an engine control circuit for controlling an accelerator actuator 36 so as to enable control of the engine 1 even when the automobile is stopped. The accelerator actuator 36 regulates the accelerator system of the engine 1 so as to enable the speed of the engine 1 to be controlled to the desired level. Specifically, the speed of the engine 1 is controlled on the basis of a drive signal output by the controller 50.
The controller 50 receives a load current detection signal from the connector box 43 and an engine speed detection signal from an ignition coil 51 for supplying ignition voltage to the spark plugs of the engine 1 and, on the basis of these signals, drives the accelerator actuator 36 so as to regulate the speed of the engine 1 to a level enabling output of electric power in an amount appropriate in light of the amount of power consumed by the load plugged into the outlet 45.
For ensuring safe regulation of the accelerator actuator 36 by the controller 50, the misoperation prevention circuit of the controller 50 receives a hand brake status signal and connector status signals, and on the basis of these produces a first misoperation prevention signal disabling the accelerator actuator 36, a second misoperation prevention signal for producing an audible alarm and the like.
The connector box 43 may be omitted where a system controller 52 is constituted by a unit comprising the inverter 44 and the controller 50 and has a construction such that the high voltage output from the generator is controllable when being input to the system controller 52.
However, since the generator apparatus separately provided in the automobile is used solely for supplying electric power to external loads and the air conditioning system is arranged in the conventional manner, the power supplied to the compressor of the air conditioner is dependent on the engine speed.
More specifically, since the engine speed is low immediately after starting, compressor operation is inadequate for achieving the target temperature to which the automobile interior is to be controlled. Further, as the temperature of the engine cooling water is low immediately after the engine is started, it will not be possible to heat the interior of the automobile by turning on the heater.
On the other hand, while the automobile is being driven, the compression cycle of the compressor becomes shorter and the output of the air conditioning apparatus is forced to a high level even though this may not be desired. As a result, the car interior tends to be overheated or overcooled, pointing up the difficulty of maintaining a pleasant car interior temperature with an air conditioning apparatus that is directly driven by the engine.
Moreover, the compressor is mounted on the engine and consequently vibrates together with it. It thus becomes necessary to use flexible rubber hoses for feeding refrigerant to the compressor from a heat exchanger fixed on the automobile body and for feeding refrigerant from the compressor to a condenser fixed on the automobile body. Because of this, there is a risk of refrigerant escaping into the atmosphere as a result of hose breakage or deterioration.
In air conditioning apparatuses which use Freon gas as the refrigerant, oil seals are used for sealing the rotating shaft of the compressor. The Freon gas tends to leak gradually from the vicinity of the oil seals and small amounts of Freon gas also find their way to this region form the rubber hoses, so that a large amount of the gas is allowed to escape into the atmosphere over extended periods of use. This is particularly undesirable in view of the deleterious effect of Freon gas on the earth's ozone layer. Then when the automobile is junked, the hoses connecting the compressor with the condenser and the heat exchanger are generally severed as part of the disassembly process, resulting in the release of additional large amounts of Freon gas into the atmosphere.